1. Field of the Invention
The present invention relates to a hybrid vehicle and a control method of the hybrid vehicle. More specifically the invention pertains to a hybrid vehicle equipped with an internal combustion engine and with a motor that is capable of outputting power to an axle, as well as to a control method of the hybrid vehicle.
2. Description of the Prior Art
A proposed hybrid vehicle has an engine, a planetary gear unit that includes a carrier linked with a crankshaft of the engine and a ring gear linked with a drive shaft mechanically connected to an axle, a first motor that inputs and outputs power from and to a sun gear of the planetary gear unit, a second motor that inputs and outputs power from and to the drive shaft, and a battery that supplies and receives electric power to and from the first motor and the second motor (see, for example, Japanese Patent Laid-Open Gazette No. 10-326115). This prior art hybrid vehicle specifies a driving power demand according to the observed accelerator opening and the observed vehicle speed, specifies a charge-discharge power according to the state of charge (SOC) of the battery, specifies a vehicle power demand based on the specified driving power demand and the specified charge-discharge power, and sets a required output from the engine. In the case of a small vehicle power demand, this prior art hybrid vehicle is driven with output of power from the second motor to the drive shaft connected to the axle while the engine is at a stop. In the case of a large vehicle power demand, on the other hand, the hybrid vehicle is driven while the engine is in operation and the power from the engine is subjected to torque conversion and is output to the drive shaft accompanied with charge and discharge of the battery.